1. Field Of The Invention
The invention relates to a one step method for the preparation of alkylphenols from phenol and the corresponding olefin. More particularly it relates to a one-step method for preparation of alkyl phenols by reacting phenols and the corresponding olefins over a catalyst comprising a heteropoly acid, homogeneous or deposited on a support. The method is especially effective in the synthesis of the most desirable para-alkyl phenol, para-nonylphenol, from phenol and nonene.
2. Description Of The Related Art
It is known in the art to prepare higher molecular weight alkylphenols, such as p-tert-octylphenol, p-nonylphenol and dodecylphenol by alkylating phenol with diisobutylene, propylene trimer and propylene tetramer, respectively, under acidic conditions. Nonylphenol, in particular, is used as an intermediate for surfactants, as well as antioxidants and in lube oil additives.
In "Bisphenol A and Alkylated Phenols", SRI PEP Report No. 192 (Dec. 1988)., page 4--4, it is reported that it is known in the art to prepare various alkylphenols by acid catalyzed reactions of phenols with various olefins. These alkylphenols may include p-tert-butylphenol, p-isopropylphenol, p-sec-butylphenol, p-tert-octylphenol, nonylphenol and dodecylphenol. The alkylation reaction takes place at or near atmospheric pressure in the presence of an acidic catalyst such as a mineral acid, a Lewis acid (e.g. boron trifluoride) or a cation exchange resin (e.g. styrene-divinyl benzene resin). The acid catalysts lead to predominantly para-alkylated phenol when the para position is available. Generally a molar ratio of phenol to olefin of 1.5-3:1 is desired to minimize the yield of dialkylphenols.
U.S. Pat. No. 4,198,531, to BASF, discloses a process for continuous manufacture of p-alkylphenols by reacting phenol with olefin at 70.degree.-140.degree. C. in a fixed bed of an organic sulfonic acid cation exchange resin.
A Lewis acid or Bronsted acid catalyst is employed in U.S. Pat. No. 4,096,209 to Ciba-Geigy to prepare a phosphorylated butylated phenol/phenol ester mixture.
In U.S. Pat. No. 2,684,389 to Gulf R & D a phenol and monoolefin are mixed in the presence of a silica-aluminum adsorbent catalyst at 137.degree. C. A silica-alumina catalyst is also employed in U.S. Pat. No. 3,876,710 to Hitachi to produce PTBP from phenol and isobutylene.
A BF.sub.3 catalyst is used for of phenol and isobutene in British Patent 1,294,781 to Hoechst where the product cooled to form crystals which are crushed before ammonia is added to remove the catalyst. British Patent 1,249,571 is related.
In German Offen. 3,443,736 to Huels the catalyst is a sulfonated polystyrene ion exchange catalyst. U.S. Pat. No. 4,461,916, also to Huels, discloses a two-stage approach for producing p-tert-octylphenol using an acid ion exchange resin. U.S. Pat. No. 4,236,033 and U.S. Pat. No. 4,168,390 to Huels also disclose ion exchange resins, the latter comprising a LEWATIT.RTM. resin deactivated with Al.sub.2 (SO.sub.4).sub.3.
British Patent 2,120,953 to lCl discloses a process for producing nonylphenol by reacting diisobutene with phenol in the presence of a catalyst comprising fuller's earth with alkyl or aryl phosphate or phosphate ester.
U.S. Pat. No. 3,872,173 to Progil discloses the reaction of gaseous isobutene with liquid phenol in the presence of an acid-activated clay, again in two steps.
A highly acidic aryl sulfonic acid catalyst is employed in U.S. Pat. No. 3,932,537 to react phenol with isobutene under anhydrous conditions.
U.S. Pat. No. 3,422,157 to Union Carbide employs a cation exchange resin catalyst.
British Patent 1,314,623 to Union Rheinische Braunkohlen discloses an activated, acid-free, bleaching earth catalyst.
In U.S. Pat. No. 4,260,833, to UOP, phenol and isobutylene are reacted at 250.degree. C. in the presence of a lithiated alumina catalyst. U.S. 3,929,912 discloses a more general alkylation of phenol and olefins in the presence of hydrogen fluoride and carbon dioxide.
An aluminum phenoxide catalyst is used for the orthoalkylation of phenol with butene-1 in French Patent 2,296,610, and U.S. Pat. No. 3,766,276, to Ethyl, as well as U.S. Pat. No. 3,933,927.
A boron trifluoride catalyst is used for the alkylation of phenol in U.S. Pat. No. 3,317,612.
Activated earth and phosphoric acid are used in a liquid phase transalkylation process in British Patent 1,444,935.
Acids are also useful for the condensation of phenol with acetone. Representative acids include an aromatic sulfonic acid (German Offen. 2,811,182 and U.S. Pat. No. 4,387,251), a volatile acid catalyst (U.S. Pat. No. 2,623,908), a strong mineral acid such as HCl or H.sub.2 SO.sub.4 (U.S. Pat. No. 2,359,242), hydrochloric acid (U.S. Pat. No. 4,517,387), H.sub.2 SO.sub.4 or HCl and 2-(4-pyridyl)ethanethiol (Japanese Kokai 57-118528), concentrated HCl (Japanese Kokai 60-38335) and hydrogen chloride (U.S. Pat. No. 4,169,211).
Of the known processes for producing alkylphenols, generally the processes require two stages for cooling and recycling and many of the catalysts are not stable at high temperatures. In addition, it is often difficult to obtain high para- to ortho- ratios or to obtain, (in the case of nonylphenol synthesis) more monononylphenol relative to dinonylphenol, while from the art it would appear that conversions of about 80% are about the most which could be expected in any process to prepare alkylphenols.
Although heteropoly acids (HPA) and their salts have been known and studied for over 160 years, the interest in their catalytic properties only developed about 20 years ago.
In an article titled "Heterogeneous Catalysis by Heteropoly Compounds of Molybdenum and Tungsten", by M. Misono, Catal. Rev. Sci. Eng., 29. 269 (1987) there is a review of the use of heteropoly acids in synthetic organic chemistry. The heteropolyanions are polymeric oxoanions which are formed by the condensation of more than two different oxoanions (Eq. (1)]. EQU 12WO.sub.4.sup.2- +HPO.sub.4.sup.2- +23H.sup.+ .fwdarw.(PW.sub.12 O.sub.40).sup.3- +12H.sub.2 O (Eq. 1)
Polyanions consisting of one kind of oxoanion are called isopolyanions (Eq. (2)]. EQU 7MoO.sub.4.sup.2- +8H+.fwdarw.(Mo.sub.7 O.sub.24).sup.6- +4H.sub.2 O (Eq. 2)
Acidic elements such as Mo, W, V, Nb and Ta are present as oxoanions in aqueous solutions and polymerize to form polyanions at low pH. The acid forms of these species are called heteropoly and isopoly acids, respectively. A variety of polyanion structures are known. Among these the so-called Keggin structure is a common form which can be represented by PW.sub.12 O.sub.40.sup.3-, a 12-heteropoly anion (XM.sub.12 O.sub.40). The central atom or heteroatom, X, can be P, As, Si, Ge, B, etc. and most of the peripheral atoms, which are called poly or addenda atoms (M), are W or Mo.
The heteropoly compounds display certain advantageous characteristics, among which are the following:
1. The catalyst design is based on acidic and redox properties which can be controlled by the constituent elements of polyanions and counteranions. PA0 2. They can provide a molecular design for solid catalysts, cluster models, or mixed-oxide catalysts. PA0 3. These catalysts provide a unique reaction field.
a. The Pseudoliquid phase can be studied using spectroscopy, stoichiometry, etc., and changes on the surface are homogeneously magnified through the bulk. PA1 b. The polyanions are soft bases which stabilize the reaction intermediates in the pseudoliquid phase.
Heteropoly acids are much stronger than the oxoacids of constituent elements and ordinary mineral acids. For example, three protons of the acid forms of PMo.sub.12 and PW.sub.12 are completely dissociated in dilute aqueous solutions. The strong acidity is caused by: (1) dispersion of the negative charge over many atoms of the polyanion and (2) the fact that the negative charge is less distributed over the outer surface of the polyanion owing to the double-bond character of the M=O.sub.t bond which polarizes the negative charge of O.sub.t to M.
In organic media, the stepwise dissociation is often observable and the acid strength measured in acetone has been found to show the following order: EQU PW.sub.12 &gt;PW.sub.11 V&gt;PMo.sub.12 .about.SiW.sub.12 &gt;PMo.sub.11 V.about.SiMo.sub.12 &gt;&gt;HC1, HNO.sub.3 (Eq. 3)
The acid strengths estimated from the formation constants for complexes of polyanions with chloral hydrate are in the order: EQU PW.sub.12 &gt;PMo.sub.12 &gt;SiW.sub.12 .about.GeW.sub.12 (Eq. 4)
The acid strength tends to decrease upon reduction or partial substitution of Mo.sup.6+ or W.sup.6+ by V.sup.5+ owing to an increased negative charge. The thermal stability of the elements constituting a polyanion vary and generally the thermal stability is W&gt;Mo and P&gt;Si.
The catalytic function of solid acids is closely related to the acidic properties (amount, strength and type of acid sites) of the catalyst surface. Ibid, p. 287, there is a discussion of five mechanisms which are possibly the origins of acidity.
Though there has been a long history of studies on acid catalysis of heteropoly compounds, it was only recently demonstrated for well-characterized solid heteropoly acids that they are much more active than ordinary solid acids. Catalytic tests reported indicate that heteropoly compounds are efficient for reactions of oxygen-containing molecules (water, ether, alcohol) such as dehydration, etherification, esterification and related reactions at relatively low temperatures. Although they are active for alkylation and transalkylation, it is reported that deactivation during these reactions is significant.
Ibid, p. 291, additional experimental factors are mentioned which show that some catalytic reactions actually proceed in bulk. Further, when heteropoly acids were dispersed on silica gel, the dispersion effect was great in the case of surface-type reaction, but the effect was small for bulk type reaction, although there was less difference at higher temperatures.
In an article titled "Advances in Catalysis by Heteropolyacids," by I. V. Kozhevnikov, Russian Chem. Revs., 56, 811 (1987), there is a discussion of the acid properties of heteropoly acids in solutions and in the solid state, their proton structure and the characteristic features of the homogeneous and heterogeneous acid catalysis.
In the same article there is a review of the description of the Keggin structure, established as early as 1934, and it is noted that it is fairly stable and is preserved in heteropoly acid catalyzed hydration-dehydration and dissolution processes, in substitution reactions of the metal, and in not too extensive oxidation-reduction reactions.
In addition the authors discuss acidic properties of heteropolyacids, including the non-localised hydrated protons and the non-hydrated protons localised at the peripheral oxygen atoms of the polyanion; the nature of the acid centres; the relative acid strengths of the crystalline acids, ibid, p. 814; the dissociation constants of heteropolyacids in water and other solvents; and p. 816, the redox potential of Keggin's structure of heteropoly compounds in aqueous solution.
The HPAs have high Bronsted acidity which is superior to usual acid catalysts and exhibit high stability in the solid state. Tungstic acids are apparently preferred because of their higher acidity, hydrolytic and thermal stability and lower oxidation potentials, in comparison with the molybdenum and vanadium-based acids.
Ibid, p. 817, there is a table of reactions catalysed by heteropoly acids. HPAs are, for example, very active and selective homogeneous catalysts for the decomposition of cumenyl hydroperoxide.
HPA and their salts can also be used as massive and deposited catalysts. In terms of catalytic properties in relation to molecules of polar substances, massive HPA resemble zeolites to some extent. In both cases, virtually all the acid centres of the catalyst are accessible. On p. 821, ibid, it is stated massive HPA's exhibit purely Bronsted acidity. In terms of strength, they are superior to aluminosilicates and, at least in the dehydration of propanol, are much more active than zeolite HY. HPA's have been employed for the industrial synthesis of t-butyl methyl ether from isobutene and methanol, see Ibid. p. 823.
An article by T. Saito in Spec. Chem., 4, pp. 35-6 (1984) focuses on the utilisation of the acid-base and redox characteristics of heteropoly acid catalysts.
An important property of HPA's is their stability. In particular there exists a stable pH region for each anion. Some anions may be converted to a more stable species or decomposed in lower pH regions.
HPAs also exhibit anomalous catalytic activities in various organic synthesis, which suggests not only the contribution of acid-base and redox properties of an inorganic nature but also the existence of interactions between HPAs and organic substrates.
A spectroscopic study on the interaction of HPA anions and proton or organic substrates demonstrates that the HPA anions are too large to be susceptible to solvation and hence can be regarded as a base of low surface charge density. In many catalytic processes involving HPAs, the interaction of the HPA anions with organic substrates as well as protons cannot be ignored.
The effect of supports such as silica, alumina, amorphous aluminosilicate and magnesia on the activity of heteropoly acids for reactions requiring strong and very strong acid sites has been studied and reported in "Catalytic Activity of Supported Heteropoly Acids for Reactions requiring Strong Acid Centres," by K. Nowinska et al., J. Chem. Soc. Faraday Trans., 87, 749 (1991).
In this study there was an attempt to evaluate the effect of different supports on HPA activity for reactions requiring acid centres of different strength. The reaction used in the test was cumene cracking. The most efficient catalyst systems for cumene cracking at 250.degree. C. appeared to be 12-tunstophosphoric acid/.gamma.-alumina followed by 12-tungstophosphoric acid (HPW)/silica whereas HPW/MgO was inactive. The authors believed their results indicate that the mounting of HPA's on silica and .gamma.-alumina considerably increased the activity for reactions occurring via a carbonium ion mechanism. On p. 751, ibid, there is a comparison of the catalytic activity and how it is affected by the percentage of loading on the supports.
Of the reactions described in the art which use heteropoly acids as catalysts there does not appear to be any work where homogeneous or heterogeneous HPA's were used in the synthesis of an alkylphenol from phenol and the corresponding olefin. In particular, there is nothing in the art which would suggest the synthesis of nonylphenol with very high selectivities and yields, and high selectivities to desirable para-nonylphenol, under adiabatic conditions using certain heteropoly acids, either solubilized in the nonene/phenol reactants or bonded to suitable oxide supports.
It would be a distinct advance in the art if alkylphenols such as nonylphenols and particularly para-nonylphenols could be prepared in one step with conversion of nonene as high as 91%. It would be particularly desirable if the catalyst exhibited high thermal stability. Such a process would be especially attractive commercially if the system were operated adiabatically, since close temperature control, cooling and recycling make many processes considerably more expensive to build and operate.
It is an object of the instant invention to provide a one-step process for the synthesis of alkylphenols in high yield and with almost complete conversion of olefin using a catalyst system which can operate under adiabatic conditions and exhibits stability even at elevated temperatures. Another object is to obtain high selectivity to desired alkylphenol while, at the same time, producing a high ratio of para- to ortho- alkylphenol products.